Mating disruption, emergence forecasting, mass trapping, control of insect pests in a predetermined area and the like can be accomplished by the sustained release of a pheromone substance, an attractant, a repellent or the like. As a method of sustainably releasing a volatile substance which is effective for insect pest control, over a long period of time, a method of sustainably releasing a volatile substance in liquid form, a method of sustainably releasing a volatile substance in gel form and other methods are known. For example, Patent Document 1 discloses a method comprising the steps of enclosing a volatile substance in a polymer vessel and sustainably releasing it from the polymer surface through the polymer wall; Patent Document 2 discloses a method comprising the steps of forming a volatile substance into a fluid gel and sustainably releasing the gel through a polymer film; and Patent Document 3 discloses a method comprising the steps of entrapping a volatile substance in a polymer lattice and sustainably releasing it in a solid or gel form.